Yeesh....I don't think there is much you can do now. Good luck in the first round of the playoffs. I'm not sure if it's close to you, but I have a friend who coaches at New Trier HS in the north suburbs of Chicago. I've seen his team play a few times, and was shocked at the level of lacrosse that is being played in Illinois. The team that I coach is a mix of football players, hockey players, and wrestlers. Most of them didn't even pick up a lacrosse stick until their freshman or sophomore year. We spent the entire first three weeks of practice doing conditioning and working on fundamentals (i.e., passing and catching, proper ground ball technique, dodging, shooting, and proper defensive technique).
The key is designing your offensive and defensive schemes to capitalize on the strengths of your players. There are only a few players on my team with adequate stick skills, but a whole group of tremendous athletes who are aggressive and can run by people with the ball in their stick.
When I started implementing my offense this year, I taught the kids a basic 2-3-1 triangle motion offense. I also drew up 4-5 plays to run out of that set. Well, I quickly learned that that scheme was too reliant on effective passing and catching. We would get the ball on offense, drop a pass, and the other team would quickly transition leaving our defense winded. The idea is ball/clock control for a team that is lacking stick skills.
I switched to a very simple 2-2-2 offense, put my 2 best attackmen behind goal line extended, an attackman and middie on the crease, and the 2 best midfielders on each line up near the top of the restraining box. Essentially, this scheme is less reliant on passing and catching, and more reliant on a 2 man pick and roll game with dodging, shooting, and feeding the crease. We really try to slow it down and control the clock. It gives the defense rest, and sometimes lulls the opposing defense to sleep. Gradually, I have been introducing some simple plays to run out of the 2-2-2, and the kids are starting to pick up on it.
Stick skills and athleticism are the name of the game in the sport of lacrosse. Most of my guys play wall ball for an hour after school, lift weights, and then meet the captains down on the field for shooting drills. We're not a great team (below .500 record), but we can play with most teams around here with the exception of the prep schools that recruit all over new england. Tell your kid and his friends to get on the wall every day this summer and focus especially on using their off-hand, go to lacrosse camps, and play in summer field/box leagues. The more you play the better you get.
Sounds like the coach might be in a little over his head....